Interest groups are seen as key intermediaries between citizens and policymakers and as central to effective democratic citizen representation in increasingly fragmented and complex political systems. However, in many instances groups fail to efficiently fulfil this role and are either characterized by “astroturf/grasstops” involvement, or prioritize close professionalized relations with public authorities (over a strong grassroots base). In this paper, we examine these claims by operationalizing and assessing the democratic potential of interest groups. We focus our analysis on European Union (EU) governance, where the linkage role of interest groups is even more critical given the representative distance. Drawing on new primary and bespoke data from a large-scale survey of groups active at the EU level, we consider both the claims groups make related to internal responsiveness, and the organizational processes and structures they have in place to connect with their constituencies. Furthermore, we also examine how relations with public authorities, in particular government funding and access to policymakers, shape, structure or potentially inhibit, the democratic potential of interest groups. We discuss the implications of our findings regarding the possible contribution of interest groups to stakeholder engagement and good governance in the EU.